Transformation models for effective friction angle and relative density calibrated based on generic database of coarse-grained soils

This study compiles a generic database of seven parameters, including relative density and friction angle, for coarse-grained soils from 176 studies, covering a wide range of reconstituted and in situ coarse-grained soils. This database, labeled as SAND/7/2794, is dominated by data from laboratory reconstituted soils such as Erksak, Hokksund, Monterey, Ottawa, Sacramento River, Ticino, and Tonegawa sands. About 15% of the data points in the database are in situ samples obtained from tube sampling, block sampling, or ground freezing techniques. The correlation behavior among some parameters in the database is consistent with existing transformation models in the literature. Mine tailings, volcanic soils, railroad ballast, gravelly soils with significant cobble or boulder content, and soils with high fines contents are removed from the database because they exhibit inconsistent behavior. Soils subjected to very high effective stresses are also removed from the database. The generic database is adopted to calibrate the bias and variability of existing transformation models. Transformation uncertainties are characterized based on their bias, variability, and the range of applicability.